Seems like life is a palindrome
Cry when you die, cry when you're born
In between it's all about the ups and downs
Add them all together, they'll cancel each other out
— Glen Phillips, from "Duck and Cover"

Using a steamer basket set over simmering water, steam the cauliflower "rice" for about 6 minutes, until tender.

Meanwhile, line a "jellyroll pan" (sheet pan with a rim) with parchment paper, and butter the parchment. Preheat the oven to 350f.

Line a colander with a thin dishtowel. Carefully dump the steamed cauliflower (but not the steaming water) into the lined colander. Gather the edges of the cloth, when the cauliflower is cool enough to handle, and squeeze out any liquid.

In a large bowl, combine the cauliflower, oregano, salt, and egg. Mix well, and dump onto the parchment lined sheet pan.

Press the mixture into a flat crust shape (slightly rectangular works well), about 1/4" thick.

Bake for 40 minutes.

Carefully slide the pizza crust from the parchment paper onto a cooling rack. Allow to cool for up to 3 hours.

When you're ready to top the pizzas, gently put the crust back onto the parchment; spread the sauce evenly and thinly over the top, and put the toppings evenly and thinly over that.

Return to a preheated 400f oven for ten minutes or so, or until the sauce is quite hot and the toppings are cooked as much as you like. Sprinkle the cheese evenly on top, and return to the oven only until the cheese is slightly melted (30 seconds or so), if you want to preserve its raw-ness. (Otherwise, melt until goopy and perfect!)